Magnetic Field Interactions of Copper-Containing Intrauterine Devices in 3.0-Tesla Magnetic Resonance Imaging: In Vivo Study

Long-acting reversible contraception methods, such as intrauterine devices (IUDs), provide the highest contraceptive efficacy and rates of satisfaction and continuation compared to other contraceptive methods (1-3). Copper-containing IUDs (e.g., Cu 380A) have shown excellent contraceptive effectiveness (3, 4), with a rare rate of dislocation (5). IUDs have been recommended as the first-line contraceptive methods offered (1), particularly for women with contraindications to different pharmaceuticals (6) and for cancer survivors (7). Diagnostic imaging with several different modalities in these patients with IUDs is possible (8), including magnetic resonance imaging (MRI).

Magnetic resonance imaging is an increasingly powerful imaging method. The new generation of 3.0-T scanners has been used more often in the clinical routine for several years now, and these scanners offer various advantages due to high spatial resolution and improved signal-to-noise ratio, leading to an improvement in the diagnostic yield (9-14). However, safety concerns about imaging metallic implants, such as copper-containing IUDs, have arisen with the higher field strengths, and devices proven to be safe at 1.5-T need to be evaluated again in a 3.0-T magnetic field environment. Dislocation, torsion, and perforation of the uterine wall, leading to unintended pregnancies, bleeding, and pelvic inflammatory disease (PID), may be caused by field interactions. The copper utilized in these devices might also lead to susceptibility artifacts and interfere with image quality, resulting in less optimal diagnostic efficacy.

Several publications indicate that copper-containing IUDs are safe for women scanned on a 1.5-T system (15-18). Zieman and Kanal (19) evaluated the Copper T 380A IUD in a 3.0-T system ex vivo. No magnetic field interactions and no risk for dislocation or migration were found. The temperature elevation of the IUD was reported to be minimal. Furthermore, artifact testing showed only small artifacts. However, there are still no data in vivo with regard to safety conditions and the presence and impact of artifacts with these IUDs. Therefore, the aim of this study was to evaluate the magnetic field interactions of copper-containing IUDs in vivo in patients examined at a 3.0-T field strength.

The results of our in vivo study suggest that MR imaging of women with a copper-containing IUD at a 3.0-T field can be performed safely. Nevertheless, this study did not allow us to exclude any complications due to field interactions.

That only half of the patients consulted a gynecologist to check the correct position of the IUD demonstrated the patients' confidence in modern imaging techniques and in the ex vivo data about the safety of metallic implants. Of the patients who did not consult a gynecologist, none reported any subjective signs of complications, such as bleeding, an infection, or an unintended pregnancy.

One patient was referred for an adverse event after the MRI examination. The gynecological check-up revealed a dislocation and partial perforation of the IUD into the fundal myometrium. However, it is unclear whether this complication was induced by magnetic field interactions. Complications like bleeding, PID, and dislocation of IUDs have been described in the literature (2, 5, 21), with higher IUD-associated complication rates in adolescents than in adults (22). A perforation through the uterine wall into the abdominal cavity is rare and may be the result of mechanical force applied during the insertion procedure of the IUD; this event also may be generated by uterine contractions or surgical intervention after insertion (23, 24), and has been reported in several case reports and case series (24-27). The incidence of perforation ranges from 1.3 to 2.2 of 1000 insertions of IUDs (24, 28, 29). We cannot be certain that, in our one case of dislocation, the device was actually in situ before the MRI examination. Considering the literature and the fact that this patient had another two 3.0-T MRI examinations at intervals of six months after the initial MR exam, with no dislocation of the device in the gynecological check-up, we assume that this complication was probably not induced by magnetic field interactions. However, this cannot be proven by the recent data and field interactions are possible, regardless of which part of the body needs to be examined. A clinical study with a larger study population that can avoid limiting factors, such as a lack of information about the implanted copper-containing devices, and about the correct position of the device before the MRI examination, is needed, before all safety concerns about copper IUDs in 3.0-T MRI are resolved.

International databases (20, 30) have been established to provide required information about the MRI safety of medical devices at different magnetic field strengths. Four different copper-containing IUDs were rated as "MR-safe" at a 1.5-T field (20), including the NOVA T 380. Ex vivo data about the safety of the copper IUD T 380A (19) led to the status "Conditional 5" at a 3.0-T field in non-clinical testing. "Conditional 5" means that the advice is acceptable for women undergoing MRI if specific guidelines or recommendations, given at the website of MR-safety and by the manufacturer, are followed (20). All women were examined according to these guidelines, even if the name and the manufacturer of the device were not known, resulting in adequate safety conditions and an excellent image quality.

Zieman and Kanal (19) described ex vivo small-sized, image-distorting susceptibility artifacts and suggested that these artifacts would cause no significant impairment of clinical image quality. However, there were no in vivo data about these artifacts and it was not known whether the artifacts would lead to a signal loss in the nearby endometrium in clinical imaging (19). The recent in vivo data confirmed that suggestion by Zieman and Kanal: no susceptibility artifacts were detected on routine clinical images. High-quality MR images of the female pelvis, particularly of the endometrium and myometrium, can be performed safely at 3.0-T without obscuring any relevant anatomical or pathological information.